The present invention relates to a substrate treating apparatus for use with glass substrates (base plates) for liquid crystals and photomasks, etc. on the surfaces of which thin films, such as of a photoresist coating solution, a photosensitive polyimide resin and dyestuffs for color filters, are to be formed. The apparatus supplies a given treating liquid to the principal planes of those substrates for desired treatment.
It has been known as conventional technology in treating apparatus for a substrate that has been subjected to certain treatment in a preceding step to be treated with a chemical and then carried to the next step after being cleaned with cleaning water. Such a substrate treating apparatus generally comprises an apparatus body including a chemical treatment station, a water cleaning station and a drying station arranged in series, and substrate carrying means provided to extend through the chemical treatment station, water cleaning station and drying station. A substrate is treated while being carried by the carrying means through the chemical treatment station, the water cleaning station and the drying station in the order named.
Specifically, certain chemical treatment is first performed on the substrate in the chemical treatment station by supplying various chemicals such as alkaline cleaning chemical, developer, etchant and remover to the top and bottom surfaces of a substrate. Then, after removing the chemical, a water cleaning process is performed on the substrate in the water cleaning station. Finally, a drying process is performed in the drying station by e.g., spraying air to the substrate.
When the substrate is carried from the chemical treatment station to the water cleaning station, there is the possibility that the substrate subjected to certain chemical treatment in the chemical treatment station is not completely free of the chemical on the top and bottom surfaces thereof. If such substrate is carried to the water cleaning station without incomplete removal of the chemical, chemical residuals are introduced to in the cleaning water in the water cleaning station, thereby contaminating the cleaning water which is circulated along a circulation passage for repeated use. As a result, usability of the cleaning water is reduced.
To avoid such a problem, an air knife is provided on a boundary between the chemical treatment station and the water cleaning station to allow gas in the form of an air curtain to be sprayed onto the top and bottom surfaces of the substrate. With this arrangement, chemical residuals on the top and bottom surfaces of the substrate are removed therefrom to such an extent that chemical residues do not dry on the surfaces of the substrate. Thus, intrusion of chemical into the water cleaning station is prevented.
In the water cleaning station, to perform a water cleaning process completely, such process is performed at two stages, i.e., in a first water cleaning section and a second water cleaning section.
When treating large sized substrates, it is often the case that a cleaning process in the first cleaning section and a cleaning process in the second cleaning section proceed simultaneously while the same substrate is being carried through the first and second water cleaning sections. That is, cleaning water (first cleaning water) is supplied to an upstream portion of the substrate carried in the first water cleaning section with respect to the substrate carrying direction (or simply referred to as a F-direction), while at the same time, another type of cleaning water (second cleaning water) is supplied to a downstream portion of the substrate carried in the second water cleaning section with respect to the substrate carrying direction (F-direction).
In such case, since the first cleaning water and the second cleaning water are supplied to the substrate at the same time, it is unavoidable that the first cleaning water mixes with the second cleaning water on the principal planes of the substrate. As a result, although desirable accurate replacement of the cleaning water is not executed on a boundary between the first water cleaning section and the second water cleaning section.
To solve the above drawback, space (intermediate zone) is provided at the boundary between the first water cleaning section and the second water cleaning section, and in this intermediate zone no process is performed on the substrate being carried by the carrying means. When the intermediate portion of the substrate passes through the intermediate zone, supplying of the first and second cleaning water is temporarily suspended. However, to make this arrangement, it is necessary to extend the water cleaning bath constituting the water cleaning station by the space corresponding to the intermediate zone, thus extending the whole length for the water cleaning bath. This leads to another problem, increasing cost of the facility.
To solve the drawback resulting from supplying the first and second cleaning water, simultaneously an air knife is provided at the boundary between the first and second water cleaning sections to spray gas toward the substrate being carried on the boundary. In this case, however, there is the possibility that the surface of the substrate will be dried partially by the gas ejected from the air knife. When the surface of the substrate is dried a certain part, stains are liable to be generated on the dried part, and such stains cannot be removed even by the water cleaning process. Accordingly, after the substrate is subjected to drying, it is highly likely that particles are generated from the stains, thus making it difficult to produce substrates free of contaminants.
To solve the above drawbacks, the applicant of this invention has proposed a substrate treating apparatus, see Japanese Patent Application No. HEI 8-88247 wherein cleaning water is ejected toward the top and bottom surfaces of a substrate from a water ejector comprising a pair of top and bottom ejectors arranged at one lateral end of the substrate in a direction normal to the substrate carrying direction (the F direction).
With this arrangement, streams of cleaning water ejected from the water ejector at a high fluid rate across the top and bottom surfaces of the substrate from the one lateral end to the opposite lateral end. This increases the effect of cleaning and smooth removal of the cleaning water from the surfaces of the substrate. Thus, this arrangement is effective in replacing cleaning water at the boundary between the first and second water cleaning sections without necessitating a larger sized water cleaning bath. This arrangement is also effective in suppressing generation of stains on the top and bottom surfaces of the substrate since there is no need for providing an air knife. However, in the apparatus of Japanese Patent Application No. 8-88247, water pressure for ejecting cleaning water is set at a relatively high level because the rear side ejecting means has an eject port oriented upward with a certain inclination angle to eject cleaning water toward the rear surface of the substrate. Due to the upward directing eject port of the rear side ejecting means, a phenomenon is likely to occur that cleaning water ejected toward the rear surface of the substrate drips down therefrom, due to the gravity, while running down the bottom surface, so the cleaning of the entire bottom surface is incomplete. To prevent such phenomenon, a high pressure cleaning water supply system must be provided.